OBJECTIVE: Glucagon-like peptide-1 (GLP-1) is rapidly inactivated by dipeptidyl peptidase 4, but may interact with vagal neurons at its site of secretion. We investigated the role of vagal innervation for handling of oral and iv glucose. Design and methods: Truncally vagotomised subjects (n=16) and matched controls (n=10) underwent 50g oral glucose tolerance test (OGTT)±vildagliptin, a DPP-4 inhibitor (DPP-4i) and isoglycaemic iv glucose infusion (IIGI) copying the OGTT without DPP-4i. Results: Isoglycaemia was obtained with 25±2 g glucose in vagotomised subjects and 18±2 g in controls (P